A federal judge has blocked enforcement of a California law restricting violent video games, saying it violates the First Amendment's guarantee of freedom of expression.

U.S. District Judge Ronald Whyte ruled late Wednesday that the state law, signed by Gov. Arnold Schwarzenegger in October, unconstitutionally restricts minors' rights to information and granted the video game industry's request for a preliminary injunction.

"Serious questions are raised concerning (California's) ability to restrict minors' First Amendment rights in connection with exposure to violent video games, including the question of whether there is a causal connection between access to such games and psychological or other harm to children," Whyte said in a 17-page opinion (click here for PDF).

California is one of a string of states that recently have enacted similar laws restricting violent and sexually explicit video games--legislation that has been uniformly rejected by the courts. Laws in Illinois and Michigan were blocked by federal judges on First Amendment grounds in the last few weeks, and earlier laws in Indianapolis and Missouri's St. Louis County have also been shot down. The U.S. Supreme Court has not squarely addressed this topic, but it has said in other contexts that even minors have free-expression rights.

The California law said minors must be restricted from buying a "violent video game." That was defined as a game in which the player has the option of "killing, maiming, dismembering or sexually assaulting an image of a human being" in offensive ways.

The Entertainment Software Association, a Washington, D.C.-based trade group that filed many of the lawsuits, applauded the California decision.

"For the sixth time in five years, federal courts have now blocked or struck down these state and local laws seeking to regulate the sale of games to minors based on their content, and none have upheld such statutes," ESA president Douglas Lowenstein said in a statement.

Because Judge Whyte's decision is only preliminary, the final outcome could change after a full trial takes place. Attorneys for California are expected to cite research that claims to demonstrate a causal link between violent video games and harm to children.